Multiple trace oscillograph system



Nov. 12, 19.40. F. H. sHEPARD, JR 2,221,115

MULTIPLE TRACEA OSCILLOGRAPH SYSTEM Filed June 50, 1937 5 Sheets-Sheet lATTORNEY AAAAAAA INVENTOR A FRANC/S l. SHED/1,90, JR. BY [f/ /W'VCA/ n,STM Q AAAAAAAA vvvvvvvvv RAAAAA Nov. 1-2, 17940.

F. H. SHVEPARD, JR

MULTIPLE TRACE OSCILLOGRAPH SYSTEM AAAA AAAL VVyVVVV R27 INVENTOR 7 WVM/l ATTORNEY SWEEP INI e Ol/Pl/T I l IGA/AL I OUTPUT EXT.'

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5 Sheets-Sheet 5 ATTORNEY -INvENToR FRANC/5 H. SHEPARD, Je. BY V ALLAAAAA VVV VVV F.A H. SHEPARD, JR

Filed June so, 1937 VVVVVVVV MULTIPLE TRACEI OSCILLOGRAPH SYSTEM Url@EXT.

Nov. l2, 1940.

Nov. 12, 1940. F. H. sHE'PARD, .1R 2221,115

' MULTIPLE TRACE OSCILLOGRAPH SYSTEM Filed June 50, 1937 V5She-ets-Sheet 4 u El:g. 6 Y I C53 ATTORN EY Nov. l2, 1940. F. H.SHEPARD, JR 2,221,15

MULTIPLE TRACE OSCILLOGRAPH SYSTEM Filed June 50, 1957 5 Sheets-Sheet 5INVENTOR F/VC/S H. .$HEPARD, JR.

x vfw/ ATTORN EY 25 A further object .Patented Nov. 12, 1940 MULTIPLETRACE OSCILLOGRAPH SYSTEM v Francis H. Shepard, Jr., Rutherford, N."J.,assignor to Radio Corporation of America., a, corporation of DelawareApplication June-3o, 1937, serial N. `151,169 1s claims. (ci. ivi-95).

The present invention relates to a circuit for` use primarily withcathode ray oscillographs in which a plurality of variables ortransients may y be observed simultaneously. This observation is 5obtainable by the provision of means for supplying signals from thepluralityl of sources in anyl U n use-i selected order to an observationoscillograph. When these signals are so 'applied in the'chosen sequence,they become visible upon the screen or y 10 target of the cathode raytube in rapid succession. y The effect of simultaneous signalapplication is obtainable by virtue of the rapidity of switching v andthe time lag of light decay from the lumi- `i5 nescent target, as wellas the period of persistence of vision, it being understood, of course,that the switching rate is so selected as to be repeatedv tubeoscillograph will permit observation of a plurality of varying signalsor transients simultaneously. v'

nately switching from one signal source to an.- other at a rate of from10 or less to 10,000 or more times per second.

30,000 or more cycles per second.

-ate with the frequency ofl either of the `input signals.

duce a system wherein the switching circuit may be operated insynchronization with an external and entirely independent 'source ofimpulses and/or where desired, in accordance with'the` frequency of apower supply source when A.'C. operation is selected.

A still further purpose of my invention is to produce a system whereinthe saw-tooth sweep or deecting voltage for the cathode ray tubev isrelation with the switch and-:also in which the amplitude of the sweepwill remain constant' over the entire frequency range of the system.

, Other purposes and uses of the device will beof the invention is toproduce a switching circuit which is capable of alter- A further objectof the present invention is to produce a circuit which is capable ofamplifyingAv uniformly and without distortion signal voltagesr which mayvary in frequency from 10,000/t0" lA still further purpose of myinvention y y produce a system in whichthe switching^ may bevsynchronized and so interlocked as to `oper- A further purpose of myinvention is to prosupplied and wherein this Voltage will always be inexact synchronization and in proper' phase choke with afcon'd y thecathodevcon f come more apparent and immediately suggest themselves tothose' skilled in the art to which `vthisinvention relates from thefollowing description ofthe circuits used, particularly when ,con-

sideredwith the "drawings, which:v

"g. YLrepresents'one formof my invention'v for y l connectionwith` acathode ray tube oscillograph, and, if l Figufres 2'through'6 show.various modied or alternative forms ofmy invention which-may be used'to4accomplish broadly the same'results.

Inv Figurefl, ve discharge ,tubesv serving as switching and/or controldevices, are used to accomplish the purpose of this invention.v Theswitching voltage is generated b'y a pair of gas triodes I and II.'I'hese triodesgbecause of the manner in which they are inter-connected,function inr a manner similar to that of a relaxation oscillationgenerator. The grid of tube I0 is connected to the anode of tube II byway of-condenser CIU and similarly the control electrode of tube II isconnected to the anode of tube I0 by wayof condenser CII. To the anodesof each source of positive potential'is connected to these f resistancesand `lcondensers byvway of the reg.sistance RI j and th Hltl.` Thefrequen" Adio-frequency choke coil o theg switching voltages upplied`byj'these tubes he condensers CIII czondensers rmay be order I toy-varyv the frei n Anadju'stmentof resistt l's the frequency aswill'later The [control grids in each of and sweep imp s `become appatheftubes are Acl necte through resistances RII) and RII tn th ar" bl'resistance RIZ, which latter resistan'c cff ,'Safpotentiometerconnected acros'"the an vde urrent vsupply `whereby the grid bias of'each ofrthe tubes ,I0 rand II may be varied.

The frequency oscillationI` of the tubes 'I0 and lII may also becontrolled-.or"synchronized by an external source through thetransformerjTl.

'I'he actual sweep voltage is obtained with the aid of an additionaltube I2 Ywhich `may be in v'the form of a twin diode. With eachswitching operation ofy thetubes I0 and II a voltagevfariation iscausedto ex tgacross the choke HIO. The twin diode i'vslconnecte'd inparallel with this 'er'Cllfwhich is inserted in s Atio'nl 1 The impulsesas applied to the choke reftherefore impressed upon the condenser CI4 tosuccessively charge the same, this condenser being intermittentlydischarged at a relatively constant rate through the resistance RI 6 andthe voltages derived therefrom are impressed upon the horizontal beamdelecting means of the cathode ray tube by way of the coupling condenserCI5 and the terminal X.

A conventional cathode ray tube is shown ai I, the tube having ,a raydeveloping means or electron gun 2. Plates 3, 4, 5 and 6 are shown forelectrostatically deiiecting the beam after it has been developed, theplates 3 and 4 operating to produce horizontal deflection of the beamwhen proper voltages are applied thereto and the plates 5 and 6operating to produce vertical deflection of the beam. A fluorescentscreen 1 is provided whereby movements of the electron beam may beobserved. It is to be understood that the particular tube shown is onlyby way of example since. obviously, other forms of cathode ray tubes maybe used and the electrostatic deflecting means may be replaced byelectromagnetic means or a combination of electrostatic andelectromagnetic deiiecting means.

A pair of tubes I3 and lI4 are also used and these tubes may be in theform of pentagrids in which the suppressor or #5 grid is connected'internally tothe cathode of the tube. It will be noticed that the gridsof the tubes I0 and II are connected to the oscillator or #3 grids ofthe tubes I4 and I3, respectively, in order that the latter tubes may bealternately biased beyond cut-off in synchronism with the operation ofthe tubes I0 and II. The two sources of signal input are impressedacross the resistances IRII and IRI2, to which, by an adjustablecontact, the #1 grids of the tubes I3 and I4, respectively, areconnected. 'I'he anodes in each of the two tubes are tied together andare connected to the positive source of potential by way of resistanceRI8. Likewise the two screen grids of the tubes are connected to thepositive source of potential by way of resistance RI1. 'I'he values ofthese resistances RI1 and RIB are so chosen that appropriate voltageswill be applied to the screen grids and the anodes of each of the tubesI3 and I4. The signal output of these tubesis applied to'the verticalbeam deflecting means of the cathode ray tube by way of the condenserCI1 and the terminal X.

It will therefore be apparent that as tubes I Il and II alternatelybecome conductive to supply the sweep voltage, the two tubes I3 and I4are likewise alternately made conductive or non-conductive insynchronism therewith, so that the signal input voltage variations arealternately made visible on the screen of the cathode ray tubeoscillograph at a frequency determined by the frequency of operation ofthe tubes I IJ and I I. 'Ihe amplitude of the sweep, that is, thehorizontal component ci' the image on the cathode ray tube, may becontrolled by varying the condenser CI4 and the resistance RIS while theamplitude of the signal, that is, the vertical component of the image onthe cathode ray tube oscillograph screen, may be varied by adjusting theresistances IRI I and IRI2.

Figure 2 shows a modified form of my invention wherein only four tubesare used. The tubes 20 and 2| are triodes and operate to supply theswitch voltage and the sweep voltage. Their alternate operation issimilar to the operation of tubes I0 and II of Figure 1, and thefrequency of their operation may be controlled by varying the size ofcondensers C20 and C2I, together with a variation in the size of theresistances R22 and R23. Ihe grids of the tubes 2li and 2| areinterconnected by the resistance R25 over which an adjustable contact ismovable. Connected to this contact is a condenser C24 through which thesweep voltage is applied to the cathode ray tube.

The tubes 22 and 23 operate as ampllers for the input -signals and arebiased to cut oil.' alternately in synchronism with the operation oftubes 20 and 2I since the #3 grid of the tubes 22 and 23 are connectedrespectively to the grids of tubes 20 and 2l. 'Ihe signal input voltagefrom the two sources is applied to the #1 grid of the tubes 22 and 23 ina manner similar to that shown and described in connection with thecircuit shown in Figure 1.

'I'he screen grids of the tubes 22- and 23 are connected together byresistance R21 and the positive source of potential is connected to anadjustable point along this resistance by way of the resistance R29.

The system shown may be caused to oscillate in synchronism with anexternal synchronizing voltage and in which case the switches SI and S2are placed in the position marked Ext, on the drawings, in which casethe external synchronizing impulses are supplied to the cathodes of thetubes 20 and 2I.

For internal synchronizing, the switches SI and S2 are placed in thealternate position marked Int. on the drawings. When such a connectionis made, the screen grids of the tubes 22 and 23 are connected to thecathodes of the tubes 20 and 2I by way of condensers C22 and C23,respectively.

This system has the advantage over the system shown in Figure 1 that theduration or percent of time that each function is amplified may becontrolled by adjusting the potentiometer R24. By such adjustment, thelength of time that one of the tubes 20 or 2I isconductive as comparedto the length of time that the other tube is conductive, may be changedwith the ell'ect that 4the horizontal component of the two signalsources as they appear on the screen of the oscillograph may bediii'erentially controlled.

Furthermore, in this system, the amplitude of the sweeps for the twofunctions can be diiTerentially adjusted by varying the contact alongthe resistance R25. By such adjustment, the length o1' the horizontalcomponent of the images as they appear on the oscillograph may be varieddiierentially.

A further advantage of this system is that the level of the zero linesof the two functions can be differentially adjusted by moving thecontact along the resistance R21. This has the eiect of diii'erentiallyvarying the voltage of the screen grid of the tubes 22 and 23 wherebythe two signals, as they appear on the oscillograph, can be made toappear about the same axis or about two axes one above the other. Thisis a desirable characteristic, particularlyv when two or more switchunits are combined to observe several functions simultaneously since thevarious functions maybe isolated by vertical displacement.

Figure 3 shows another form of my invention. This system is in many waysthe same as the system shown in Figure 2 with the difference that thetubes 30 and 3| are triple grid tubes. the suppressor grid beingconnected externally to the cathode of each tube. The use of the threegrid tubes improves the operation of this circuit in that the sweepvoltage is lof a truer saw-tooth form and as a result the rate of sweepof the beam 'across the screen in thefoscillograph. is mor -uniforml/'It will be noticed that tnesynchmnizing 1mpulses for the tubes 30.and,f3|, regardless of whether they are derivedfrom an internal or anscreen is not strictly uniform'. Wherethis effect is particularlyobjectionable,the circuit shown in Figure 3 should then be used. Thesameadjustments that arepossible in Figure 2 with respect l vto theduration and amplitude of the sweep as `well as the zero base lines ofthe functions, are

alsopossible in the circuit shown in Figure 3.

Figure 4 shows a relatively vsimple two-tube electronic switch, sweepand amplifier in which the tubes are identical and. maygbe. ofthe penta.

grid type. In this circuit 'th` fubesnotonly act as a source of switchvoltage ,y d sweep voltage, but also' operate as' amplifie v fo'rthe twoinput voltages. The frequency of opcrationof the system may of course bevcontrolled by varying the size of the condensersUC4`0z`and C4I,together with the size of the resistacesR43 and R44. In this system,thev input voltages'are applied to the oscillator or #3y grid of reachof the tubes and at the time one of the tubes isoperating to supply thesweep voltage the same tube is also operating to amplify the inputvoltage and to apply the same to the vertical A,defiecting means of thecathode ray tube. The sweep voltage is supplied to the horizontaldeflecting means of the cathode ray tube through the condenser C244which is connected by an adjustable contact to the potentiometerresistance R42 which inter-connects the controlgrids of the two tubes. fIn this circuit there is a slight tendency for th switch to lock in stepwith either or both of the signals and there is a tendency for a part ofthe signal to appear on the sweep. Both of these effects are due to thenegative trans-conductance between the #3 grid and the screen grids 2and4 of the tubes. The latter effect is particularly noticeable whenviewing a ylarge number of signal cycles on one sweep cycle. Both ofthese effects are more noticeable with large input signals and both canbe reduced by reducing vthehfinput signals (adjusting the resistances1R41 and 1R42), or by increasing the value of the common plate load toashigh as is consistent with the desired amplier frequencyrespons'e. Thecommon plate Y load vis represented by the resistance R48.

affected as little as possibleby the varying charg-v ing current to thegrid of the other stage. To

yaccomplish this v the screen load resistor R41 should be made as low aspossible. It is also essential that the potential of the #1 grid beconstant during the amplifying part of the cycle for each tube and vthisis accomplishedby means of the grid current limiting resistors R40 andR4L l It is possible` with this circuit to ydifferentially adjust theamplitudes of the sweeps .for the two 4functions by varying theresistance R42, to differentially adjust the duration of the sweeps forthe two functions by varying the resistance R45, and also to. raise orlower the zero lines of the two functions by adjusting the resistanceR41. These adjustments operate in the same manner as do thecorresponding adjustments given above with respect to the disclosureshown in Fig. 2.

Figure 5 shows a circuit similar to the circuit shown in Figure 4 withthe exception that a duo-r v diode is used to improve the wave form andlncrease the amplitude of the sweep circuit and to increase theoperating frequency of the system. With the type system shown it ispossible to operate up to '750,000 cycles per second. If lt is desired,and by proper compensation, it is possiblev that this frequency may beconsiderably extended. Y

The system disclosed in Figure 5 diers from that shown in Figure 4 inthat the resistances R43, R44, R45 as well as theresistance R42, areomitted and the first grids of the pentagrids are connected eachrespectively to the cathodes of the duo-diode. The anodes of this tubeare connected together and supply the sweep output by Way of condenserC54. The source of anode potential for the duo-diode is connectedthrough the variable resistance R52. The remainder of the system isthesame as that shown in Figure 4 and further explanationis believed to beuns IleCeSSaly.

slight tendency for the switch to synchronize with either or both of theinput signals and is sufficient in most cases to maintain the operationof the device in synchronization with the signalv variations if such isdesired. The condensers C60 and CBI are preferably made adjustable inorder that the frequency of the devicemay be controlled in order tocause the circuit -to operate at a predetermined frequency or tomaintain the circuit operating yin synchronization with uctuations ofthe input of the one or the other of the input signals. The resistancesR63 and R64 are generally adjusted when the capacitances of thecondensers C60 and C62 are changed in order to improve this control.

By varying the resistance R65 i-t is possibletol differentially controlthe duration or percentage of time that each function is amplified inorder that the magnification of the horizontal comf ponent of the imageformed on the oscillograph ,may be increased or decreased as desired.*.Also,

by adjusting the resistance R62 it is possible to differentially varythe amplitudes of the successive horizontal sweeps.

The resistances R68 and R69 are for thepurl pose of maintaining properpotentials uponithe electrodes of the tubes and the load resistances R66are so chosen as to keep the gain constant during the amplifying part ofthe cycle for each stage.

From the above description of the circuits shown, it may be seen that acathode ray -tube oscillograph may be used to observe two or morefunctions simultaneously, the functions appearing on the screenalternately and in rapid succession. The circuits used are relativelysimple and do not entail the vuse of -a large' number of CFI . a shorttime lag being used when high frequenirl tubes nor a complicated circuitfor producing the results.

When a cathode ray tube of the type shownin connection with Figure 1 isused, as it maybe with any of the circuits shown in the drawings. thetime lag of light decay of the luminescent target may be varied inaccordance with the frequency of the sweep impulses, a target havingcies are employed and a target having a longer time lag being used whenlower frequencies are employed. l

It is to be understoodthat various modincations may be made in any orall of the systems disclosed without departing from the spirit and scopeof the invention, and it is desired that only such limitations be placedon the device as are necessary in view of the prior art and the appendedclaims.

I claim as my invention: l

1. A system for controlling a cathode ray tube oscillograph comprising asweep output, a signal output and a pair of signal input circuits, meansincluding a pair of discharge tubes for supplying rapidly'recurringsweep impulses to the sweep output, means including a second pair ofdischarge tubes for amplifying the signals from the input circuits,means to control the operation of said last named means by said ilrstnamed means whereby the amplified signals are supplied to the signaloutput in succession and in synchronism with the sweep impulses, andmeans for differentially controlling the duration or percent of timethat each signal is amplied.

2. A system for controlling a cathode ray tube oscillograph comprising asweep output, a signal output and a pair of signal input circuits, meansincluding a pair 0f discharge tubes for supplying rapidlyyrecurringsweep impulses to the sweep output, means including a second pair ofdischarge tubes for amplifying the signals from the input circuits,means to control the operation of said last named means by said rstnamed means whereby the amplified signals are supplied to the signaloutput in succession and in synchronism with the sweep impulses, andmeans for differentially controlling the duration of alternate sweepimpulses independently of the amplitudes of the impulses.

3. A system for controlling a cathode ray tube oscillograph comprising asweep output, a signal output and a pair of signal input circuits, meansincluding a pair of discharge tubes for supplying rapidly recurringsweep impulses to the sweep output, means including a second pair ofdischarge tubes for amplifying the signals from the input circuits,means to control the operation of said last named means by said ilrstnamed means whereby the amplified signals are supplied to the signaloutput in succession and in synchronism with the sweep impulses, andmeans for differentially controlling the amplitudes of alternate sweepimpulses.

4. A system for controlling a cathode ray tube oscillograph comprising asweep output, a signal output and a pair of signal input circuits, meansincluding a pair of discharge tubes for supplying rapidly recurringsweep impulses to the sweep output, means including a second pair ofdischarge tubes for amplifying the signals from the input circuits,means to control the operation of said last named means by said rstnamed means whereby the amplified signals are supplied to the signaloutput in succession and in synchronism with the sweep impulses, andmeans for dierentially adjusting the zero base lines` of the amplifiedsignals.

5. A system'for controlling a cathode ray tube oscillograph comprising asweep output, a signal output and a pair of `signal input circuits, apair of electron discharge tubes each having a plurality of controlelectrodes, means for individually impressing the input signals upon onecontrol electrode of each of the tubes, respectively, and circuit meansincluding another control electrode of each tube for rendering the tubesalternately conducting and non-conducting in rapid succession wherebysweep impulses are supplied to the sweep output and whereby theamplified signal impulses are alternately supplied to the signal output.

6. A system for controlling a cathode ray tube oscillograph comprising asweep output, a signal output and a pair of signal input circuits, apair of electron discharge tubes, means for impressing the input signalsupon a control electrode of each of the tubes respectively, means forrendering the tubes alternately conducting and nonconducting in rapidsuccession whereby sweep impulses are supplied to the sweep output andthe amplied signal impulses are alternately supplied tothe signaloutput, and means for diierentially controlling the duration or percentof time that each signal is amplified.

7. A system for controlling a cathode ray tube oscillograph comprising asweep output, a signal output and a pair of signal input circuits, apair of electron discharge tubes, means for impressing the input signalsupon a control electrode of each of the tubes, respectively, means forrendering the tubes alternately conducting and non-conducting in rapidsuccession whereby sweep impulses are supplied to the sweep output andthe amplied signal impulses are alternately supplied vto the signaloutput, and means for differentially controlling the duration ofalternate sweep impulses independently of the amplitudes ofthe impulses.

8. A system for controlling a cathode ray tube oscillograph comprising asweep output, a signal output and a pair of signal input circuits, apair of electron discharge tubes, means for impressing the input signalsupon a control electrode of each of the tubes, respectively, means forrendering the tubes alternately conducting and non-conducting in rapidsuccession whereby sweep impulses are supplied to the sweep output andthe Aamplied signal impulses are alternately supplied to the signaloutput, means for dinerentially controlling the duration of alternatelyconducting and non-conducting periods and means -for differentiallycontrolling the amplitudes Yof alternate sweep impulses, said two lastnamed meansbeing independently operable.

9. A system for controlling a cathode ray tube oscillograph comprising asweep output, a signal output and a pair of signal input circuits, apair of electron discharge tubes, means for impressing the input signalsupon a control electrode of each of the tubes, respectively, means forrendering the tubes alternately conducting and non-conducting in rapidsuccession whereby sweep impulses are supplied to the sweep output andthe amplified signal impulses are alternately supplied to the signaloutput, and means for differentially controlling the amplitudes ofalternate sweep impulses. y

10. A system for controlling a cathode ray tube oscillograph comprisinga sweep output, a signal output and a pair of signal input circuits, apair of electron discharge tubes, means for impressing the input signalsupon a control electrode of each of the tubes, respectively, means forrendering the tubes alternately conducting and non-conducting in rapidsuccession whereby sweep impulses are supplied to the sweep output andthe amplified signal impulses are alternately supplied to the signaloutput, and means for differentially adjusting the zero base lines ofthe amplified signals.

11. A system for controlling a cathode ray tube oscillograph comprisinga sweep output, a signal output and at least a pair of signal inputcircuits, means including a 4pair of discharge tubes for supplyingrapidly recurring sweep impulses to the sweep output, means including asecond pair of discharge tubes for amplifying the signals from the inputcircuits individually, means whereby the operation of the last namedmeans is controlled by said first named means to supply the signals ltothe signal output in succession and in synchronism with the sweepimpulses, and means whereby said rst pair of tubes may be operated insynchronism with an external source of impulses.

l2. A system for controlling a cathode ray tube oscillograph comprisinga sweep output, a signal output and a pair of signal input circuits,means including a pair of discharge tubes for supplying rapidlyrecurring sweep impulses to the sweep output, means including a secondpair of discharge tubes for amplifying the signals from the inputcircuits, means to control the operation of said last named means bysaid first named means whereby the amplified signals are supplied to thesignal output in succession and in synchronism with the sweep impulses,and means whereby said rst pair of tubes may be operated in synchronismwith the frequency of the one or the other of said input signals.

13. A system for controlling a cathode ray tube oscillograph comprisinga sweep output, a signal output and a pair of signal input circuits,means including a pair of discharge tubes for supplying rapidlyrecurring sweep impulses to the sweep output, means including a secondpair of discharge tubes for amplifying the signals from the inputcircuits, means to control the operation of said last named means bysaid rst named means whtreby the amplified signals are supplied to thesignal output in succession and in synchronism with the sweep impulses,and means whereby said rst pair of tubes may be operated in synchronismwith an external source of impulses or in synchronism with the frequencyof the one orthe other of said input signals.

14. A system for controlling a cathode ray tube oscillograph comprisinga sweep output, a signal output and a pair of signal input circuits,means including a pair of discharge tubes for supplying rapidlyrecurring sweep impulses to the sweep output, means'including a secondpair of discharge ,tubes for amplifying the signals from the inputcircuits, means to control the operation of said last named means bysaid first named means whereby the amplified signals are supplied to thesignal output in succession and in synchronization with the sweepimpulses, means for differentially controlling the duration of alternatesweep impulses, and means for differentially controllingy the amplitudesof alternate sweep impulses, lsaid two last named means beingindependently operable.

15. A system for controlling a. cathode ray tube oscillograph comprisingelectronic means for producing rapidly recurring sweep impulses, aplurality of separate input circuits, means for successively switchingfrom one input signal to another in synchronism with the sweep impulses,said last named means being under the control of said first named means,and means for differentially controlling the duration of alternate sweepimpulses.

`16. A system for controlling a cathode ray tube oscillograph comprisingelectronic means for producing rapidly recurring sweep impulses, aplurality of separate input signals, means for successively switchingfrom one input signal to another in synchronism with the sweep impulses,vand means for differentially controlling the amplitudes of alternatesweep impulses.

17. A system for controlling a. cathode ray tube oscillograph wherein aplurality of signals may be caused to appear simultaneously comprisingmeans for electronically producing a series of rapidly recurring sweepimpulses, means whereby the signals may be independently andsuccessively applied to the tube in synchronism with the sweep impulses,and means for differentially adjusting the zero base lines of thesignals.

18. A system for controlling a cathode ray tube oscillograph wherein aplurality of signals may be ycaused to appear simultaneously comprisingmeans for electronically producing a series of rapidly recurring sweepimpulses, means whereby the signals may be independently andsuccessively applied to the tube in synchronism with the sweep impulses,means for diirentially controlling the duration of alternate sweepimpulses, and means for differentially controlling the amplitudes ofalternate sweep impulses, said two last named means being independentlyoperable.

